U.S. Pat. No. 4,625,712 and copending application Ser. No. 129,713 filed Dec. 7, 1987 disclose miniature high-speed blood pumps which can be threaded through a blood vessel to provide rapid heart assist without major surgery. These blood pumps are driven from outside the body by a flexible cable encased in a cable sheath attached to the pump. The cable is powered by an electric motor, and the cable sheath also serves as the purge fluid supply to the hydrostatic purge seal and bearings of the pump.
Three specific problems are produced by this environment: for one, the entire purge fluid path and cable must be sterilizable and disposable; secondly, any debris produced by the abrasion of the sheath by the cable must not be permitted to enter the pump; and thirdly, the motor must be firmly positionable on the patient so as to cause the least possible discomfort, and to keep the cable as steady and straight as possible, after the blood pump and cable sheath have been threaded through the vascular system.